The invention relates in particular but without implied limitation to the separation of lignins and sugars in an extracted liquor which is obtained from a process for the production of paper pulp, lignins, sugars and acetic acid and which is described in European Patent EP-B1-1 180 171 (or U.S. Pat. No. 7,402,224).
Such a process, among other extraction processes, in particular starting from a lignocellulose starting material, makes it possible to obtain, in addition to a solid fraction constituting the paper pulp of the organic phase, an organic phase comprising in particular, in solution, monomeric and polymeric sugars and lignins resulting from the initial plant starting material.
In the context of the recovery in value of all the products obtained by such a process, it is important to be able to separate the lignins from the sugars as completely as possible, without denaturing the quality of the lignins.
This is also done in order to avoid obtaining, according to various known techniques, a “pulp” formed of lignins which exist when lignin “grains” are “stuck together by” sugars.
The various known processes make it possible in particular to industrially obtain degraded and sulphur-comprising lignins (the presence of sulphur being due to the production process).
“Kraft” lignins are concerned in particular.
Another process known from the document EP-1 686 138 provides a process for the separation and recovery of an acid/sugar liquid phase from a lignocellulose starting material. However, this process does not make it possible to separate the lignins and thus not without degrading them, since, in this process, the lignins are agglomerated to give a “lignophenol derivative” product obtained during the process by impregnation of the starting material using a “phenol derivative”.
The present invention is targeted at providing a separation process, in particular one which is highly effective in an acidic medium, which avoids any phenomenon of agglomeration of the lignin particles, that is to say which prevents the formation of aggregates composed of lignins and sugars.